Custom manager for ordering Django QuerySets with modeltranslation

managers.py

from django.db.models import F, QuerySet
from django.db.models.functions import Coalesce
from modeltranslation.settings import AVAILABLE_LANGUAGES
from modeltranslation.utils import (
    build_localized_fieldname, get_language, resolution_order)


class MultilingualOrderQuerySet(QuerySet):
    def coalesce_translations(self, field):
        """Coalesce all translations of a given field according to the
        current language and fallback resolution order, and annotate
        the current QuerySet with it through a `field_translations` key.
        """
        # Languages the translation has to be searched in, in relevant
        # order
        langs = resolution_order(
            get_language(), {'defaut': AVAILABLE_LANGUAGES}
        )
        # Build the list of translated fields names in relevant order
        fields = [
            build_localized_fieldname(field, lang) for lang in langs
        ]

        # If there is only one relevant field, no coalescing is needed
        if len(fields) == 1:
            annotation = F(fields[0])

        else:
            # Get the underlying model field type
            FieldType = self.model._meta.get_field(field).__class__
            # Annotate needs to know which type of field it has to output,
            # because translated fields type differs from usual Django
            # fields (e.g. TranslatedCharField differs from CharField)
            annotation = Coalesce(*fields, output_field=FieldType())

        return self.annotate(
            **{field + '_translations': annotation}
        )

    def order_by_translated(self, field):
        """As `modeltranslation` does not provide fallback values when
        using the `order_by` method of its manager, this method
        implements it.

        It provides ordering with fallbacks, for a single translated
        field only.
        """
        return (
            self
            .coalesce_translations(field.lstrip('-'))  # Strip order
            .order_by(field + '_translations')
        )